1. Field of the Invention
This invention relates to a pipe connecting structure to be used for a milk delivery pipe of a pipe line milker system, said structure comprising a milk tap and a plug-in metal fitting.
2. Prior Art and the Objects of the Invention
Any known milk tap to be used for a milk delivery pipe in a pipeline milker system has a circular aperture having a diameter which is the same as that of the milk delivery pipe in order to secure an airtight connection of the pipe and the milk tap.
However, two types of milk delivery pipes are currently marketed, those with a larger diameter and those with a smaller diameter, and selectively used depending on the size and scale of the facility. Hence suppliers of milk taps are required to market two different types of milk taps, those matching with larger diameter pipes and those matching with smaller diameter pipes.
Then, the milk tap manufacturer always has to have two different types of molds at hand in order to produce two different types of milk taps. Obviously, it is more costly and time consuming to manufacture milk taps of two different types than to manufacture milk taps of the same type.
In view of this problem of the prior art, it is therefore an object of the present invention to provide an adapter that allows a single milk tap to be used with milk delivery pipes of different diameters.
As for the slide valve of a milk tap, there is known a type having a main body to be fitted to a pair of rods held by holders arranged at opposite lateral sides of the aperture of the milk tap, the main body containing in it a cylindrical valve provided with a semispherical bottom. Spring coils are arranged between the holders and the valve main body, and a pair of projections is arranged at opposite sides of the aperture of the milk tap in such a way that each of the projections contact with the semispherical bottom only at a point.
Although the designer of the slide valve having a configuration as described above must obviously have intended to prevent it from touching the milk tap except, on a surface area surrounding the aperture thereof when the valve is closed or opened, the valve slightly but inevitably touches the projections at the bottom. It is also disadvantageous that the slide valve for slidingly closing and opening the aperture of the milk tap is made heavy because it relies for sliding motion on its own weight and the negative pressure of the milk delivery pipe connected to it.
In view of the above identified problems of the prior art, it is another object of the invention to provide a slide valve to be used for a milk tap that is lightweight and does not touch the milk tap at the bottom.
Finally, as for the plug-in metal fitting of the milk tap, there is known a type disclosed in Japanese Utility Model Application Publication No. 49-26148 and Japanese Utility Model Application Laid-Open No. 58-164460 comprising a pipe which is brought into contact with the periphery of a corresponding aperture of a milk delivery pipe by sliding the fitting on a metal connector (milk tap) fitted to the milk delivery pipe.
Such a metal fitting requires two different actions of inserting its pipe horizontally into a milk delivery pipe and then sliding it vertically on a milk tap fitted to the milk delivery pipe and these actions have to be carried out successively in order to bring the fitting into the right position. Additionally, the pipe of the fitting has to be securely fit into the aperture of the milk delivery pipe by relying on the vacuum in the delivery pipe.
However, to carry out two different actions successively is obviously an cumbersome operation and, while the metal fitting relies on the vacuum in the milk delivery pipe for its connection with the periphery of a corresponding aperture of the milk delivery pipe, only a short distance is normally allowed for the metal fitting to move into the milk delivery pipe because of structural limitations. Therefore, there has been a demand for a connector assembly that can urge the pipe of the metal fitting to the corresponding aperture of the milk tap.